Updates and Regional Multidecadal Trends in Aerosol Optical Depth for All MODIS and VIIRS Sensors

Aerosol optical depth (AOD) retrievals via the Dark Target algorithm are now available for VIIRS NOAA-20 alongside an algorithm update for the existing Suomi-NPP data product, and a corresponding product for VIIRS NOAA-21 is in development. With VIIRS data records beginning in 2012, 2018, and 2023, and both Terra MODIS (launched 2000) and Aqua MODIS (launched 2002) nearing end of mission life, the best way to construct a 30-year climate data record is to maintain continuity between versions of the same algorithm run on each sensor. Although VIIRS SNPP has just over a decade in common with the MODIS sensors, all three show good agreement in depicting regional trends emerging in the AOD record. AOD has decreased by between 0.003 and 0.01 per year over eastern China, the eastern United States, much of Europe, and parts of Brazil, while increasing by roughly the same amount over India and parts of Canada. 10-year trends are easiest to distinguish in China and India, where the change in AOD over time occurs in all four seasons of each year, while other regional trends become clearer over the 20-year MODIS record.